Chapter 2: Problem 110
Use your knowledge of the slopes of parallel and perpendicular lines. Is the figure with vertices at \((-11,-5),(-2,-19),(12,-10),\) and (3,4) a parallelogram? Is it a rectangle? (Hint: A rectangle is a parallelogram with a right angle.)
Short Answer
Expert verified
The figure is a parallelogram and also a rectangle.
Step by step solution
01
Calculate the slope of each side
First, calculate the slope of the line segments formed by the vertices. Use the slope formula \[ m = \frac{y_{2} - y_{1}}{x_{2} - x_{1}} \].
02
Calculate the slope for vertices \((-11,-5)\) and \((-2,-19)\)
Plugging the values into the slope formula:\[ m_{1} = \frac{-19 + 5}{-2 + 11} = \frac{-14}{9} = -\frac{14}{9} \].
03
Calculate the slope for vertices \( (-2,-19) \) and \((12,-10)\)
Use the slope formula:\[ m_{2} = \frac{-10 + 19}{12 + 2} = \frac{9}{14} = \frac{9}{14} \].
04
Calculate the slope for vertices \( (12,-10) \) and \((3,4)\)
Again using the slope formula:\[ m_{3} = \frac{4 + 10}{3 - 12} = \frac{14}{-9} = -\frac{14}{9} \].
05
Calculate the slope for vertices \( (3,4) \) and \((-11,-5)\)
Finally, using the slope formula:\[ m_{4} = \frac{-5 - 4}{-11 - 3} = \frac{-9}{-14} = \frac{9}{14} \].
06
Determine if the figure is a parallelogram
Since the opposite sides have equal slopes (\( m_{1} = -\frac{14}{9} \) and \( m_{3} = -\frac{14}{9} \), and \( m_{2} = \frac{9}{14} \) and \( m_{4} = \frac{9}{14} \)), the figure is a parallelogram.
07
Check for right angles to see if it's a rectangle
For the figure to be a rectangle, adjacent sides must be perpendicular. Multiply the slopes of adjacent sides to see if the product is -1.\( m_{1} \cdot m_{2} = -\frac{14}{9} \cdot \frac{9}{14} = -1 \). This condition is satisfied, thus confirming that the figure has right angles.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Parallelogram Properties
A parallelogram is a quadrilateral with opposite sides that are parallel and equal in length. This means that if you calculate the slopes of opposite sides and they are equal, the figure is a parallelogram. Here’s what you need to know about parallelogram properties in detail:
- Opposite sides are parallel and have equal slopes.
- Opposite sides are equal in length.
- Opposite angles are equal.
- The diagonals bisect each other.
- Adjacent angles add up to 180 degrees.
Rectangle Properties
A rectangle is a special type of parallelogram. It has all the properties of a parallelogram but with the additional feature that all angles are right angles (90 degrees). Here are the key properties:
- All angles are 90 degrees.
- Opposite sides are parallel and equal in length.
- The diagonals are equal in length.
Slope Formula
The slope of a line measures its steepness and is calculated using the slope formula. The formula for finding the slope \(m\) between two points \((x_1, y_1)\) and \((x_2, y_2)\) is:
\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]
This formula is essential for determining whether lines are parallel or perpendicular:
\[ m = \frac{y_2 - y_1}{x_2 - x_1} \]
This formula is essential for determining whether lines are parallel or perpendicular:
- If two lines are parallel, their slopes are equal.
- If two lines are perpendicular, the product of their slopes is -1.